Solid abrasive article and method of making honing elements therefrom



July 30, 1968 w. c. CROWE 3,394,502

SOLID ABRASIVE ARTICLE AND METHOD OF MAKING HONING ELEMENTS THEREFROM Original Filed March 30, 1964 AT 7' GPA/6' VJ United States Patent O a 394 502 SOLID ABRASIVE AfrTrLE AND METHOD OF MAKING HONING ELEMENTS THEREFROM William G. Crowe, Milford, Mich, assignor to Mid-West Abrasive Company, Owosso, Mich, a corporation of Delaware Original application Mar. 30, 1964, Ser. No. 355,599, now Patent No. 3,276,170, dated Oct. 4, 1966. Divided and this application May 23, 1966, Ser. No. 552,029

Claims. (Cl. 51-204) ABSTRACT OF THE DISCLOSURE This application is a division of my copending application Ser. No. 355,599, filed Mar. 30, 1964, now patent No. 3,276,170, and relates generally to abrasive articles. More particularly, the invention refers to an elongated article from which abrasive honing elements can be severed, and to a method of severing such elements from the article.

One object of the invention is to provide an elongated article from which can be severed a plurality of honing elements for use with a honing tool which has a body provided with slots for the reception of a plurality of said elements.

Another object is to provide an elongated article comprising an elongated slab of a bonded abrasive material, and a relatively thin coating of a relatively non-abrasive material on said slab.

Another object is to provide a fill agent such as sulphur, penetrating substantially the entire body of the abrasive stick.

Another object is to provide a method of making honing elements by severing the same from an elongated article.

Other objects and features of the invention will become apparent as the description proceeds, especially when taken in conjunction with the accompanying drawing, wherein:

FIGURE 1 is a fragmentary side elevational view, with parts in section, illustrating a honing tool inserted in a bore being honed, with the abrasive elements of my invention in the slots of the tool.

FIGURE 2 is a fragmentary longitudinal sectional View of the structure shown in FIGURE 1, with parts broken away and in section.

FIGURE 3 is a perspective view of the abrasive element.

FIGURE 4 is a sectional view of the abrasive element, taken on the line 44 in FIGURES 1 and 3.

FIGURE 5 is a perspective view, with portions broken away, of an elongated coated abrasive article from which the abrasive elements may be severed in the practice of the method of the invention.

FIGURE 6 is a fragmentary side elevational View of the elongated abrasive article.

Referring now more particularly to the drawing, and especially to FIGURES 1 to 4 thereof, the honing tool is semi-diagrammatically indicated at 10 and is an elongated tubular member which is provided with a plurality of circumferentially spaced slots 14 elongated in the direction of length thereof. The honing elements 16 are of identical construction and are respectively disposed in the slots for radial expansion and retraction relative to the honing tool.

Referring to FIGURES 3 and 4, each honing element 16 comprises an elongated bonded abrasive stick 18 which is of substantial length relative to its width and thickness. As seen in FIGURES 1 and 3, the sides 20 and 22 of the abrasive stick lie in parallel planes, and the ends 24 and 26 may be rounded as shown to blend or merge smoothly with the adjacent sides 20 and 22. Actually the ends could be of some other shape. The front or working face 28 of the abrasive stick intersects the sides and ends 2026 at substantially right angles thereto and is a substantially plane surface, although it may be somewhat crowned due to the fact that it will take the curvature of the bore being honed. The rear face of the abrasive stick is designated 30 and is tapered with respect to the front face for a purpose which will be brought out more clearly hereinafter.

The abrasive stick 18 is preferably covered on all of its surfaces except its front working face 28 with a relatively non-abrasive, thin coating 32 of uniform thickness. While preferably the lead side of the stick, that is the side facing in the direction of tool rotation, is coated, it might be left uncoated because there is not as much tendency of the tool slot to wear on the lead size. The thrust or trailing side should be coated to prevent abrasion of the tool slot, and the rear face should be coated to prevent abrasion of the expansion cone which is more fully described hereinafter. Preferably the coating 32 will be of a thickness in the range of approximately .002"-.006". Actually, the coating could be any thickness up to say 5, (which expressed in decimals is .03125). The range of .002".006" is preferred, however, because more abrasive surface can be presented to the work, that is the slot is not filled up with an extra thickness of coating 32 which is non-abrasive. A thin coating, such as in the preferred range, is just as effective in preventing Wear of the tool slot or expansion cone, as a thick coating. The coating also serves to support edges, particularly the trailing edge, of the working face of the stick 18. The material covering the abrasive stick is more in the nature of a coating than a housing or casing or shell, as will be understood from an appreciation of the relatively thin nature thereof. Therefore, the article or element 16 may appropriately be called a solid abrasive article.

The coating 32 may be formed of a number of different relatively non-abrasive materials. A thermosetting resin, particularly a polyester epoxy copolymer is preferred. Also suitable is acrylic latex, which is a base for many paints. Other materials such as acrylic resin, vinyl resin, melamine alkyd, furfural acid polymer and polyvinyl acetate may be employed as the material for the coating.

Referring again to FIGURES 1 and 2, the slots 14 in the honing tool have substantially the same outline as the coated abrasive elements, to closely receive the same. In other words, the side walls of the slots are parallel and spaced apart a distance substantially equal to the width of the abrasive elements, and the ends of the slots match the ends of the abrasive elements and spaced apart a distance substantially equal to the length of the coated abrasive elements. The coated material is of a character which will have a close friction fit in the slots, so that the abrasive elements will tend to be retained in the slots and will not drop out due to centrifugal force of rotation. There is not so much friction however as to prevent the honing elements from being expanded radially outwardly by the cone 40 carried by the adjusting rod 42 which is reciprocable within the tool 10, or from being mechanical- 1y retracted. The taper of the cone corresponds to the taper on the coated rear wall of the abrasive elements, so that the cone surface has a full surface-to-surface contact with the coated rear wall of the abrasive element. Obviously when the cone 40 is moved downwardly in FIGURE 2, the abrasive elements are cammed in a radially outward direction. The coating 32, while it is non-abrasive, is of such character as to wear readily so as not to interfere with the abrasive action. The coating should wear at at least the same rate as the abrasive and preferably, as in the case of polyester epoxy copolymer, faster.

Referring to FIGURES and 6, there is shown an elongated abrasive article 50 employed in the practice of the method of making the abrasive elements illustrated in FIGURES 3 and 4. The article 50 comprises an elongated piece or slab 52 of a bonded abrasive material. The slab is of substantial length relative to its width and thickness. The fiat sides of the slab 52 are parallel to each other and spaced apart a distance equal to the width of the abrasive sticks 18. This dimension of the abrasive slab 52 is its thickness. The edges of the abrasive slab 52 are spaced apart exactly the same distance as the ends 24 and 26 of the abrasive sticks, and are shaped exactly the same. The distance between the edges of the abrasive slab 52 is the width dimension of the slab and corresponds to the length of the abrasive elements. The slab 52 is preferably completely covered on all of its side and edge surfaces with the same coating which covers the abrasive sticks. As noted, one side, corresponding to the lead side of the stick to be formed, could be left uncoated although preferably it also is covered. This coating in FIGURES 5 and 6 is indicated by the reference character 54, although it will be understood that it is the same coating, both in thickness and material as the coating 32 for the abrasive sticks.

The abrasive elements 16 are formed from the abrasive article 50 by cutting the abrasive article either transversely along lines spaced lengthwise thereof, which is preferred, or lengthwise along laterally spaced lines. Transverse cutting lines are designated 56 in FIGURE 6 of the drawing. The spacing between the lines of severing corresponds with the thickness of the abrasive elements to be formed, and it will be noted that the cutting lines are angled to provide the proper taper between the front working face and the rear face of the abrasive elements. After the abrasive elements have been severed from the elongated abrasive article 50 by transverse cutting, it will be understood that the rear face of the abrasive stick 18 will be uncoated, since it is one of the severed surfaces. Preferably, the rear face of the abrasive element thus formed will, after severing, be covered with a coating of the same thickness and material as the coating 32 on the remaining side and end surfaces of the abrasive stick. The rear face of the stick is preferably coated so as to avoid abrasion of the adjusting cone 40.

It will be understood that when the elements 16 are cut from the article 50 transversely, the length of the severed abrasive elements corresponds to the width of the article 50, the width of the severed elements corresponds to the thickness of the article 50, and the thickness of the severed elements corresponds to the spacing between the cutting lines 56.

Alternatively, the abrasive elements may be cut from the slab lengthwise, that is along the longitudinal lines of severing designated 57 and transverse lines 58. Longitudinal severing involves certain problems not involved in transverse severing. Thus the upper end of the slab in FIGURE 6 should be coated with the coating 54 before severing, and contoured to correspond with the slot ends. If not, the ends of the elements formed therefrom would have to be contoured and then coated after severing. Also the opposite ends of the upper most elements severed, and both ends of the intermediate elements severed, should be contoured and then coated after severing. Also the rear tapered surfaces of the elements which are uncoated due to severing should be coated. The front working faces of those elements which are contoured and coated should be ground down fiat to remove the coating.

Preferably, the coating is brushed or sprayed on in liquid form at or near room temperature and allowed to cure at that temperature. The polyester epoxy copolymer is well suited for this method of application Accordingly, the abrasive slab 50 can be fully treated in accordance with accepted methods involving bonded abrasives before the coating is applied and while the abrasive is exposed on all surfaces. Such. treatment involves introducing, by differential air pressure, a fill agent, such as sulphur, into the abrasive. This requires a substantial amount of the abrasive to be exposed to be successful. Heretofore, relatively thick plastic casings have been molded around the abrasive. However, the heat of the molding operation, which might run as high as 400 F. for phenolic resins, would melt out the fill agent if the treatment was applied before molding. Accordingly, it was necessary to treat after molding. Treatment after molding had the disadvantage that much of the abrasive surface was covered by the molded casing, and hence the fill agent did not adequately penetrate the abrasive. Since according to the procedures described herein, the coating is applied at or near room tem erature, the abrasive may be pre-treated, and the fill agent will not be melted out.

It will be understood therefore, that in accordance with the preferred method, the slab 50 will be treated before being coated, and also that if the elements 16, shown in FIGURE 3, are formed separately or by some other method than by severing from a slab, the elements will first be treated and then coated.

The coating on the articles is very thin and hence a maximum amount of abrasive is presented to the bore being honed. The coating material, which as noted is preferably a polyester epoxy copolymer, is unaffected by liquids that may be encountered in a honing operation, such as water, oils and kerosene. Since the coating is thin, it generates a minimum of heat by contact with the bore being honed. Excessive heat of course will distort the part being honed. The coating is extremely durable and because of its thinness allows a maximum of coolant to reach the abrasive. In order to obtain the maximum realization of these benefits and advantages, the coating will preferably be .002".006" in thickness.

What I claim as my invention is:

1. An elongated article from which can be severed a plurality of honing elements for use in the slots of a honing tool body, said article comprising an elongated slab of a bonded abrasive material of substantial length relative to its width and thickness, said slab having a fill agent therein penetrating substantially the entire body thereof, and a relatively thin liquid-applied surface coating of 'a relatively non-abrasive material on said abrasive slab, said elements being adapted to be severed from said article by cutting along spaced lines, said coating being curable at or near room temperature and of such character as to wear at least at the same rate as the abrasive when said elements are used in a honing operation while providing such frictional engagement with the walls of the slots in the hone body without abrasion of the slot walls, as to frictionally retain said elements on the tool body within the slots but permitting them to be moved outwardly by the application of a positive force.

2. The article defined in claim 1, wherein the thickness of said coating is in the range of approximately .002"- .006".

3. The article defined in claim 1, wherein said coating is formed of a thermosetting resin.

4. The article defined in claim 1, wherein said coating is formed of a polyester epoxy copolymer.

5. The article defined in claim 1, wherein said coating is plastic formed at least in part from a polyester resm.

6. The article defined in claim 1, wherein said coating is plastic formed at least in part from an epoxy resin.

7. The method of making honing elements for use in the slots of a honing tool body, comprising the steps of providing an elongated slab of a bonded abrasive material of substantial length relative to its width and thickness, treating said slab with a fill agent penetrating substantially the entire body thereof, then liquid applying a relatively thin coating of a relatively non-abrasive material to said slab so as to cover said abrasive slab on certain of its surfaces, and severing said elements from said slab by cutting along spaced lines, said coating being curable at or near room temperature and of such character as to wear at least at the same rate as the abrasive when said elements are used in a honing operation while providing such frictional engagement with the walls of the slots in the hone body with out abrasion of the slot walls, as to friction-ally retain said elements on the tool body within the slots but permitting them to be moved outwardly by the application of a positive force.

8. The method defined in claim 7, wherein said elements are severed from said slab by cutting transversely thereof along lines spaced lengthwise of said slab so that the length of the severed elements corresponds to the width of said slab, the width of the severed elements corresponds to the thickness of said slab, and the thickness of the severed elements corresponds to the spacing between the cutting lines.

9. The method defined in claim 7, wherein said ele ments are severed from said slab by cutting longitudinally thereof along lines spaced transversely of said slab so that the length of the severed elements corresponds to the length of said cutting lines, the width of the severed elements corresponds to the thickness of said slab, and the thickness of the severed elements corresponds to the spacing between the cutting lines.

10. The method defined in claim 7, including the further step of liquid-applying a relatively thin coating of said relatively non-abrasive material to one of the severed surfaces of said elements.

References Cited UNITED STATES PATENTS 2,375,263 5/1945 Upper 51 404 X 2,729,924 1/1956 Klein 51- 346 2,797,537 7/1957 Peden 51-204 ROBERT C. RIORDON, Primary Examiner.

D. G. KELLY, Assistant Examiner. 

